REGIOCHEMICALLY AND STEREOCHEMICALLY DEFINED SYNTHESIS OF ALLYLSILANES

Allyl sulfides containing a siloxy or hydroxy group at appropriate positions were successfully converted by two methods into two types of allylsilanes with almost complete stereo- and regiocontrol. In one method, an allyllithium was generated from the siloxy compound after which the silyl group migrated from oxygen to the carbanionic site. The reaction of 4-[[(trimethylsilyl)oxy]methyl]-3-methyl-2-cyclohexenyl phenyl sulfide with lithium di-tert-butylbiphenylide (LDBB) led to an exclusive formation of (1R*,2R*)-2-methyl-2-(trimethylsilyl)-3-cyclohexene-1-methanol. The second method involved the silylation of an oxyanion-carbanion. Using this method, (1R*,4R*)-1-methyl-4-(trimethylsilyl)-2-cyclohexene-1-methanol was obtained by treating its lithium alkoxide with LDBB followed by silylation with chlorotrimethylsilane.